The present invention relates to a process for producing a die usable for formation of honeycomb structure. More particularly, the present invention relates to a process for producing a die usable for formation of honeycomb structure, which can produce a die usable for forming a honeycomb structure having hexagonal honeycomb cells, easily and at a high precision.
For production of a ceramic-based honeycomb structure, there has been widely used a process which comprises extruding a clay through a die for formation of honeycomb structure, which die has, in a base material for die, backside holes for introduction of clay and slits (for example, lattice-shaped slits) communicating with the backside holes, for extrusion of clay. Ordinarily in this die, the backside holes for introduction of clay are provided at one of surfaces (clay-introducing side) of the base material for die so as to have a large opening area and, at the other (opposite) side (extrudate-leaving side) of the base material for die, slits for clay extrusion are provided, for example, in a lattice shape so as to have a small width corresponding to the thickness of each partition wall of a honeycomb structure to be produced using the die. The backside holes are ordinarily provided so as to correspond to the intersections of the slits for clay extrusion having, for example, a lattice shape and communicate with the slits inside the base material for die. Therefore, the clay made of, for example, a ceramic raw material, introduced from the backside holes moves from the clay-introducing holes of relatively large inner diameter to the slits for clay extrusion, of small width, and a formed material of honeycomb structure is extruded from the slits for clay extrusion.
For production of such a die usable for formation of a honeycomb-shaped honeycomb structure, there was disclosed, for example, a process which comprises forming slits having a hexagonal cell shape by electrical discharge machining (EDM) (JP-A-2002-273626).
In the process disclosed in JP-A-2002-273626, feeding holes (backside holes) are formed at the hole formation side of a base material for die; then, at the opposite side (slit formation side) of the base material for die are formed a plurality of preliminary holes so that the feeding holes and the preliminary holes communicate with each other; an electrode for electrical discharge machining is provided so as to face the slit formation side of the base material for die; a dielectric fluid is fed onto the slit formation side and is sent, by suction, to the hole formation side via the preliminary holes; in this state, electrical discharge machining is advanced while the discharge electrode is being moved forward; then, the machining is stopped and the discharge electrode is moved backward to expose the slits which are in the middle of formation; the dielectric fluid is injected from the hole formation side toward the slit formation side (at this time, the flow of dielectric fluid is reversed); the electrical discharge machining and the injection of the dielectric fluid in reverse flow are repeated alternately; thus, slits are formed.